/**
 *    Copyright (C) 2013 mongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

/**
 * This file contains tests for mongo/db/exec/sort.cpp
 */

#include "mongo/db/exec/sort.h"

#include "mongo/db/json.h"
#include "mongo/db/exec/mock_stage.h"
#include "mongo/unittest/unittest.h"

using namespace mongo;

namespace {


    TEST(SortStageTest, SortEmptyWorkingSet) {
        WorkingSet ws;

        // MockStage will be owned by SortStage.
        MockStage* ms = new MockStage(&ws);
        SortStageParams params;
        SortStage sort(NULL, params, &ws, ms);

        // Check initial EOF state.
        ASSERT_TRUE(ms->isEOF());
        ASSERT_FALSE(sort.isEOF());

        // First call to work() initializes sort key generator.
        WorkingSetID id = WorkingSet::INVALID_ID;
        PlanStage::StageState state = sort.work(&id);
        ASSERT_EQUALS(state, PlanStage::NEED_TIME);

        // Second call to work() sorts data in vector.
        state = sort.work(&id);
        ASSERT_EQUALS(state, PlanStage::NEED_TIME);

        // Finally we hit EOF.
        state = sort.work(&id);
        ASSERT_EQUALS(state, PlanStage::IS_EOF);

        ASSERT_TRUE(sort.isEOF());
    }

    /**
     * Test function to verify sort stage.
     * SortStageParams will be initialized using patternStr, queryStr and limit.
     * inputStr represents the input data set in a BSONObj.
     *     {input: [doc1, doc2, doc3, ...]}
     * expectedStr represents the expected sorted data set.
     *     {output: [docA, docB, docC, ...]}
     */
    void testWork(const char* patternStr, const char* queryStr, int limit,
                  const char* inputStr, const char* expectedStr) {

        // WorkingSet is not owned by stages
        // so it's fine to declare
        WorkingSet ws;

        // MockStage will be owned by SortStage.
        MockStage* ms = new MockStage(&ws);
        BSONObj inputObj = fromjson(inputStr);
        BSONElement inputElt = inputObj.getField("input");
        ASSERT(inputElt.isABSONObj());
        BSONObjIterator inputIt(inputElt.embeddedObject());
        while (inputIt.more()) {
            BSONElement elt = inputIt.next();
            ASSERT(elt.isABSONObj());
            BSONObj obj = elt.embeddedObject();

            // Insert obj from input array into working set.
            WorkingSetMember wsm;
            wsm.state = WorkingSetMember::OWNED_OBJ;
            wsm.obj = obj;
            ms->pushBack(wsm);
        }

        // Initialize SortStageParams
        // Setting limit to 0 means no limit
        SortStageParams params;
        params.pattern = fromjson(patternStr);
        params.query = fromjson(queryStr);
        params.limit = limit;

        SortStage sort(NULL, params, &ws, ms);

        WorkingSetID id = WorkingSet::INVALID_ID;
        PlanStage::StageState state = PlanStage::NEED_TIME;

        // Keep working sort stage until data is available.
        while (state == PlanStage::NEED_TIME) {
            state = sort.work(&id);
        }

        // Child's state should be EOF when sort is ready to advance.
        ASSERT_TRUE(ms->isEOF());

        // While there's data to be retrieved, state should be equal to ADVANCED.
        // Insert documents into BSON document in this format:
        //     {output: [docA, docB, docC, ...]}
        BSONObjBuilder bob;
        BSONArrayBuilder arr(bob.subarrayStart("output"));
        while (state == PlanStage::ADVANCED) {
            WorkingSetMember* member = ws.get(id);
            const BSONObj& obj = member->obj;
            arr.append(obj);
            state = sort.work(&id);
        }
        arr.doneFast();
        BSONObj outputObj = bob.obj();

        // Sort stage should be EOF after data is retrieved.
        ASSERT_EQUALS(state, PlanStage::IS_EOF);
        ASSERT_TRUE(sort.isEOF());

        // Finally, we get to compare the sorted results against what we expect.
        BSONObj expectedObj = fromjson(expectedStr);
        if (outputObj != expectedObj) {
            mongoutils::str::stream ss;
            // Even though we have the original string representation of the expected output,
            // we invoke BSONObj::toString() to get a format consistent with outputObj.
            ss << "Unexpected sort result with query=" << queryStr << "; pattern=" << patternStr
               << "; limit=" << limit << ":\n"
               << "Expected: " << expectedObj.toString() << "\n"
               << "Actual:   " << outputObj.toString() << "\n";
            FAIL(ss);
        }
    }

    //
    // Limit values
    // The server interprets limit values from the user as follows:
    //     0: no limit on query results. This is passed along unchanged to the sort stage.
    //     >0: soft limit. Also unchanged in sort stage.
    //     <0: hard limit. Absolute value is stored in parsed query and passed to sort stage.
    // The sort stage treats both soft and hard limits in the same manner

    //
    // Sort without limit
    // Implementation should keep all items fetched from child.
    //

    TEST(SortStageTest, SortAscending) {
        testWork("{a: 1}", "{}", 0,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 1}, {a: 2}, {a: 3}]}");
    }

    TEST(SortStageTest, SortDescending) {
        testWork("{a: -1}", "{}", 0,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 3}, {a: 2}, {a: 1}]}");
    }

    TEST(SortStageTest, SortIrrelevantSortKey) {
        testWork("{b: 1}", "{}", 0,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 2}, {a: 1}, {a: 3}]}");
    }

    //
    // Sorting with limit > 1
    // Implementation should retain top N items
    // and discard the rest.
    //

    TEST(SortStageTest, SortAscendingWithLimit) {
        testWork("{a: 1}", "{}", 2,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 1}, {a: 2}]}");
    }

    TEST(SortStageTest, SortDescendingWithLimit) {
        testWork("{a: -1}", "{}", 2,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 3}, {a: 2}]}");
    }

    //
    // Sorting with limit > size of data set
    // Implementation should retain top N items
    // and discard the rest.
    //

    TEST(SortStageTest, SortAscendingWithLimitGreaterThanInputSize) {
        testWork("{a: 1}", "{}", 10,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 1}, {a: 2}, {a: 3}]}");
    }

    TEST(SortStageTest, SortDescendingWithLimitGreaterThanInputSize) {
        testWork("{a: -1}", "{}", 10,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 3}, {a: 2}, {a: 1}]}");
    }

    //
    // Sorting with limit 1
    // Implementation should optimize this into a running maximum.
    //

    TEST(SortStageTest, SortAscendingWithLimitOfOne) {
        testWork("{a: 1}", "{}", 1,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 1}]}");
    }

    TEST(SortStageTest, SortDescendingWithLimitOfOne) {
        testWork("{a: -1}", "{}", 1,
                 "{input: [{a: 2}, {a: 1}, {a: 3}]}",
                 "{output: [{a: 3}]}");
    }

}  // namespace
